The uncatalyzed interconversion between para and ortho H2 increases with increasing temperature; thus rapidly condensed H2 contains large quantities of the high-energy ortho form that converts to the para form very slowly. The ortho/para ratio in condensed H2 is an important consideration in the preparation and storage of liquid hydrogen: the conversion from ortho to para is exothermic and produces enough heat to evaporate some of the hydrogen liquid, leading to loss of liquefied material. Catalysts for the ortho-para interconversion, such as ferric oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromic oxide, or some nickel compounds, are used during hydrogen cooling.
What are some catalysts used in hydrogen cooling
ferric oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromic oxide, or some nickel compounds

Melbourne has an integrated public transport system based around extensive train, tram, bus and taxi systems. Flinders Street Station was the world's busiest passenger station in 1927 and Melbourne's tram network overtook Sydney's to become the world's largest in the 1940s, at which time 25% of travellers used public transport but by 2003 it had declined to just 7.6%. The public transport system was privatised in 1999, symbolising the peak of the decline. Despite privatisation and successive governments persisting with auto-centric urban development into the 21st century, there have since been large increases in public transport patronage, with the mode share for commuters increasing to 14.8% and 8.4% of all trips. A target of 20% public transport mode share for Melbourne by 2020 was set by the state government in 2006. Since 2006 public transport patronage has grown by over 20%.
Which rail station was the world's busiest passenger station in 1927?
Flinders Street Station

The Richmond area also has two railroad stations served by Amtrak. Each station receives regular service from north of Richmond including Washington, D.C., Philadelphia, and New York. The suburban Staples Mill Road Station is located on a major north-south freight line and receives all service to and from all points south including, Raleigh, Durham, Savannah, Newport News, Williamsburg and Florida. Richmond's only railway station located within the city limits, the historic Main Street Station, was renovated in 2004. As of 2010, the station only receives trains headed to and from Newport News and Williamsburg due to track layout. As a result, the Staples Mill Road station receives more trains and serves more passengers overall.
Along with Williamsburg, what city's rail traffic uses the Main Street Station?

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